Day 4-8 Severe Weather Outlook Issued on Nov 18, 2020
Updated: Wed Nov 18 09:29:03 UTC 2020
Day 4 Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Day 5 Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Day 6 Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Day 7 Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Day 8 Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
No Risk Areas Forecast
D4
Sat, Nov 21, 2020 - Sun, Nov 22, 2020
D7
Tue, Nov 24, 2020 - Wed, Nov 25, 2020
D5
Sun, Nov 22, 2020 - Mon, Nov 23, 2020
D8
Wed, Nov 25, 2020 - Thu, Nov 26, 2020
D6
Mon, Nov 23, 2020 - Tue, Nov 24, 2020
(All days are valid from 12 UTC - 12 UTC the following day)
Note: A severe weather area depicted in the Day 4-8 period indicates 15%, 30% or higher probability for severe thunderstorms within 25 miles of any point.
PREDICTABILITY TOO LOW is used to indicate severe storms may be possible based on some model scenarios. However, the location or occurrence of severe storms are in doubt due to: 1) large differences in the deterministic model solutions, 2) large spread in the ensemble guidance, and/or 3) minimal run-to-run continuity.
POTENTIAL TOO LOW means the threat for a regional area of organized severe storms appears unlikely (i.e., less than 15%) for the forecast day.
Forecast Discussion
ZCZC SPCSWOD48 ALL
ACUS48 KWNS 180927
SPC AC 180927
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0327 AM CST Wed Nov 18 2020
Valid 211200Z - 261200Z
...DISCUSSION...
A more progressive and active weather pattern will emerge over the
CONUS during the Day 4-8 time period. A series of mid/upper troughs
will migrate from west to east across the country, bringing chances
for thunderstorm activity to parts of the southern/central Plains
eastward to the Mid-Atlantic. The first trough will shift eastward
from the Plains to the Atlantic coast Day 4/Sat through Day 7/Tue.
The second trough will dig across the western states beginning late
Day 5/Sun and emerge over the Plains on Day 7/Tue. Strong surface
high pressure over the eastern U.S. initially will preclude much in
the way of strong Gulf return flow over the south-central and
southeast states. Given limited moisture and a pattern more typical
of anafrontal precipitation, severe thunderstorms are not expected,
though some isolated thunderstorm activity could be embedded in
periods of moderate to heavy rain from the central/southern Plains
to the Midwest through Day 5/Sun and into the Northeast on Day
6/Mon.
Another round of rain and thunderstorms is expected to develop over
the central/southern Plains as the second upper trough ejects
eastward across the Rockies around Day 7/Tue. Forecast guidance
varies in the timing and intensity of this system, so confidence is
low in the later parts of the forecast period, though some
thunderstorm potential is expected to spread eastward across much of
the eastern portions of the CONUS. Depending on low level moisture
and degree of destabilization that could occur, some low-end strong
to severe thunderstorm potential could unfold across the Southeast
by the middle of next week, but uncertainty is too great to include
probabilities at this time.
..Leitman.. 11/18/2020
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